Re: [PATCH, RFC] mlx4: Avoid that mlx4_cmd_wait() contributes to the system load

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

On 07/24/13 17:17, Or Gerlitz wrote:
> On 22/07/2013 18:23, Bart Van Assche wrote:
>> Avoid that kernel threads running mlx4_cmd_wait() contribute to the
>> system load by setting the task state to TASK_INTERRUPTIBLE instead
>> of TASK_UNINTERRUPTIBLE while waiting. This patch reduces the load
>> average from about 0.5 to about 0.0 on an idle system with one mlx4
>> HCA and no IB cables connected.
>
> Before diving to the implications of the patch, lets discuss the
> phenomena you see...
> So the load average on this idle system is 0.5 or 0.05?
>
> I don't see 0.5 or a like on my systems that are installed with HCAs and
> are idle.  Could it
> be that some IB management entity is repeatedly  sending MADs to this
> system?

Hello Or,

I saw a load of 0.5 with several different upstream kernels (3.6..3.10 
at least). The only IB-related process that was running on the system 
was opensmd. This is definitely reproducible. It was only a month after 
I had noticed this phenomenon that I started searching for the root cause.

Bart.

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